1. Field
One embodiment of the present invention relates to a presence management system enabling management of presences of users via a network, a presence notification method, a server unit, and a terminal device for use in the system.
2. Description of the Related Art
There is a service capable of sharing conditions of users in a network as one of services using an Internet Protocol (IP) network. Presences showing the conditions of users (online, offline, during telephone call, during leaving seat, during sitting on seat, etc.) are stored in a database to be managed. A user or a terminal who (that) is “a presenter of a presence” is referred to as a presentity, and a user (or a terminal) who (that) is “a browser of a presence” is referred to as a watcher.
When the conditions of the presentities vary, the fact is immediately notified to the presence server. The presence server which received the notice notifies the changes in condition of the presentities to the watchers; however, the presence server has to pay attention the timing of the notice. It is not preferable to notify the changes in condition to all the watchers at a time, because a network load and a processing load become heavy suddenly. It is all the more not preferable if the number of the watchers is large.
Jpn. Pat. Appln. KOKAI publication No. 2006-285782 has disclosed a technique for reducing the load in such a kind of system. This patent document reduces the load by not transmitting and receiving useless messages among clients and a server. However, messages described in this document mean e-mails and text data, and not messages (e.g., session initiation protocol [SIP] messages) related to the notification itself of the presences. That is, this document only has disclosed processing in an upper-layer on the assumption that the notification of the presences inter-terminal has been completed. It has been desired to reduce the load related to the transmission and reception of the messages among the presentities and the watchers in a lower-layer.
In addition, there is a technique for the watchers, like mail clients, to distribute the load by periodically requesting for presence acquisition to the server. Internet Engineering Task Force (IETF) defines to notify only difference information of the change in presence from the presence server to the watchers. However, neither of the aforementioned techniques are not drastic measures for a load distribution.
As described above, the existing presence management system is apt to increase the Toad on a system including a network and a computer facility in notifying the presence information to the watchers from the presence server. Although staggering the timing of the notice for each watcher is a possible approach, a further polished method has been desired.